Papua New Guinea's opposition leader, Belden Namah, says Australia's Manus detention centre and asylum seekers scheme is unconstitutional.
Mr Namah has told a news conference that he is seeking a Supreme Court interpretation.
He says he wants clarification on the detainees' visa, saying foreigners can only get visas for tourism, employment or business.
Furthermore he has asked the government to explain how these foreigners can be detained when they have not illegally entered PNG on their own accord or committed any crime in PNG.
The opposition leader questions why an illegal processing centre is set up in PNG when Australia has a big land mass.
The prime minister, Peter O'Neill, has dismissed the concerns, saying activities associated with the Manus asylum detention and processing centre are within the perimeters of PNG laws.
Australia reopened its Manus detention centre last year after operating it for three years from 2001 to 2004.